An embodiment relates to a naked-eye stereoscopic display apparatus having a parallax in a single dimension.
There are known technologies in which an image displayed on a display device such as a printing surface and a liquid crystal panel is divided into a plurality of viewpoint directions and presented by using a special optical member such as a lenticular lens, a slit-like barrier or a lens array. Thereby, the displayed image changes according to the position of the viewer.
As an example of one such technology, there is a technology for allowing the display image to be stereoscopically viewed in such a manner that different display images (parallax images) of the same object, which have a specific parallax therebetween, are inputted to the right eye and left eye of a person who views the display device. In accordance with this stereoscopic technology, a naked-eye stereoscopic display apparatus can be realized which enables the person to achieve stereoscopic vision without the need to wear special eyeglasses.
In the case of achieving stereoscopic vision of the image in the naked-eye stereoscopic display apparatus, there is a requirement that the number of viewpoints be increased by dividing the display image as finely as possible. This is in order to expand the visual recognition range in which stereoscopic vision can be achieved, and to obtain natural stereoscopic vision and smooth motion parallax, which are worthy of long-time viewing. Recently, in a relatively low-resolution display device such as digital signage or a car navigation device, stereoscopic vision using parallax images has been performed for the purpose of enhancing visual attraction and visibility regarding stereoscopic information. However, as the number of viewpoints is increased, the resolution feeling is lowered. Note that it is defined that a value physically owned by the display device itself is the resolution, and that the extent of the resolution sensed by a person is the resolution feeling. Even in the case of achieving stereoscopic vision of the display image on the low-resolution display device, there is a requirement that natural stereoscopic vision be realized by suppressing the lowering of the resolution as much as possible.
In order to satisfy these requirements a multi-eye type is effective, in which the viewpoints are not divided by assuming positions of eyes of an observer who observes the display device, but instead viewpoints are divided as finely as possible, and the observer views the display device at any viewpoint among the finely divided viewpoints. In order to increase the number of parallax images, it is effective to increase the lens pitch with respect to the pixel pitch of the display device, for example, in the case where the optical member to be mounted on the display device is a lenticular lens. However, owing to the magnification effect of the lens, as the lens pitch increases color pixels look larger, and accordingly, the resolution feeling of the parallax images in the pitch direction of the lens is significantly lowered. Then, a malfunction occurs in that the resolution feeling of the parallax images differs between the horizontal direction and the vertical direction. Note that the same shall also apply to the case of using an optical member such as a barrier.
As a technology for solving this malfunction, as described in Japanese Patent No. 390456 (Patent Literature 1), it is described that the periodic direction of cylindrical lenses (optical elements) which compose the lenticular lens (optical member) is inclined with respect to the horizontal direction of the pixel array of the display device. In accordance with the technology described in Patent Literature 1, one three-dimensional image is composed by using not only the pixels in the horizontal direction but also the pixels in the vertical direction, whereby the lowering of the resolution feeling in the horizontal direction in the stereoscopic display can be suppressed, and the balance of the resolution feeling between the horizontal and vertical directions can be enhanced.